1. Field of the Invention
This invention relates to a windmill provided with means for governing the speed (rpm) of a windmill rotor to provide overspeed protection in the event of extremely windy conditions or in the event of rapid change or inadvertent loss of the load demand, and more particularly to a windmill having centrifugally feathered rotors to control the speed of the rotors.
2. Description of the Prior Art
In implementing windmill technology, it is necessary to control or limit the speed (rpm) of the windmill rotors so as not to burn out and destroy an electrical or mechanical load coupled to the windmills, such as a generator or a pump (water-liquid). It is also necessary to limit the rotor speed due to high wind velocity or load disconnection so that the rotor does not overspeed and self destruct.
An early attempt at providing a wind power apparatus having wind rotated rotors mounted so as to be self-governing in terms of rotation speed irrespective of considerable variation in the wind velocity is disclosed in U.S. Pat. No. 2,054,383 to Ludewig. This patent discloses a wind power apparatus including an axle and hub assembly supporting a pair of hinged rotor blades defining a pitch which is varied in dependence upon the speed of rotation by means of the centrifugal forces generated in rotation of the blades. According to Ludewig, centrifugal forces tend to pull the rotor blade into the plane of rotation which has the effect of reducing the power output. Unfortunately, this tendency to flatten the blades in the plane of rotation does not limit the speed of rotation or reduce wind loading on the rotor blades. As a result, the prior art system disclosed in the Ludewig patent is subject to self destruction under "no load" conditions and is not adaptable for large scale windmill systems employing heavy rotor blades.
Other prior art references of interest are the following U.S. Pat. Nos. 478,945; 1,949,611; 2,037,528; 2,041,611; 2,076,520; 2,134,661; 2,253,013; 2,484,291; 4,008,006; 4,029,434; and 4,201,514.